Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Income Tax Disclosure [Abstract]

Components of Loss Before Income Taxes

The components of loss before income taxes from continuing operations were as follows for 2016, 2015 and 2014 (in thousands):

	Years Ending December 31,
	2016			2015			2014
United States	$	(105,533	)	$	(135,359	)	$	(158,390	)
Foreign	(1,386		)	(3,023		)	(2,771		)
Loss before income taxes from continuing operations	$	(106,919	)	$	(138,382	)	$	(161,161	)

Tax Effects of Temporary Differences and Carry Forwards on Deferred Tax Assets

The tax effects of temporary differences and carry forwards that give rise to significant portions of the deferred tax assets are as follows (in thousands):

	December 31,
	2016			2015
Net operating loss carry forwards	$	228,637		$	187,169
Capitalized start-up costs	7,093			7,475
Research and development credits	8,922			6,320
Stock compensation	10,256			12,683
Other	4,313			6,875
Total deferred tax assets	259,221			220,522
Valuation allowance	(255,765		)	(216,220		)
Deferred tax liability—fixed assets	(3,456		)	(3,056		)
Deferred tax liability—derivative liability	—			(1,246		)
Net deferred tax assets, after valuation allowance	$	—		$	—

Reconciling Items from Income Tax Computed at Statutory Federal Rate

Reconciling items from income tax computed at the statutory federal rate for the years ended December 31, 2016, 2015 and 2014, were as follows:

	Years Ending December 31,
	2016		2015		2014
Federal income tax statutory rate	34.0	%	34.0	%	34.0	%
State income taxes, net of federal benefits	4.5		2.2		1.6
Revalued derivative liability	—		—		0.6
Incentive stock option compensation	(0.4	)	(0.4	)	(1.3	)
Research tax credits	1.4		0.4		0.8
Other	(0.1	)	—		—
Valuation allowance	(37.5	)	(36.2	)	(35.7	)
Effective income tax rate from continuing operations	1.9	%	—	%	—	%

Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands):

Balance as of December 31, 2013	$	1,488
Addition based on tax positions related to current year	6,411
Additions based on tax positions related to prior year	4,042
Balance as of December 31, 2014	11,941
Addition based on tax positions related to current year	184
Reduction based on tax positions related to prior year	(9,799		)
Additions based on tax positions related to prior year	86
Balance as of December 31, 2015	2,412
Addition based on tax positions related to current year	595
Additions based on tax positions related to prior year	431
Balance as of December 31, 2016	$	3,438